1. Field of the Invention
The present invention relates to a method and apparatus for displacing a torque track used to guide a top drive drilling unit. More particularly, the present invention relates to a method and apparatus for displacing the lower end of a torque track which is used to guide a top drive unit to drill an oil or gas well.
2. Description of the Prior Art
It is well known in the prior art to use a top drive drilling unit to rotate the drill stem of an oil and gas well. See, for example, U.S. Pat. Nos. 4,449,596; 3,464,507; and 3,766,991 and pending U.S. application Ser. No. 050,537, filed Apr. 20, 1993. A top drive drilling unit is suspended by a cable from the crown of a mast of a drilling rig above the drill string. Essentially, the unit rotates the drill string from the top side as opposed to the use of a rotary table and related equipment at the rig floor.
A top drive unit usually requires a track which runs the length of the mast to guide the top drive, to restrain it from lateral movement and to transfer torsional loads originating from the rotary drilling operation into the derrick substructure. Such torque drive track systems are disclosed in U.S. Pat. Nos. 4,865,135 5,251,709 and pending U.S. patent application Ser. No. 217,689, filed Mar. 24, 1994.
In the process of drilling a well, it may be advantageous to disconnect the drill string from the top drive unit and handle sections of drill pipe without the top drive unit in place. In these instances, it is preferable to disconnect the top drive unit from the draw works and move it away from immediately above the drill string. See, for example, U.S. Pat. Nos. 4,421,179; 4,437,524 and 4,458,768. However, such prior designs are complex and cumbersome. If this operation can be performed in a quick and efficient manner by use of a single configuration, the amount of time required to add or remove joints of drill string can be significantly improved. Accordingly, there is a need for an improved method and apparatus for temporarily suspending the top drive and displacing it from a location immediately above the drill site to permit the draw works and other equipment to add or remove sections of drill pipe without interference by the top drive.